6(d) Students know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecosystem and how oxygen cycles through photosynthesis and respiration.

6(e)Students know a vital part of an ecosystem is the stability of its producers and decomposers.

6(f)Students know at each link in a food web some energy is stored in newly made structures but much energy is dissipated into the environment as heat. This dissipation may be represented in an energy pyramid.

4Ch. 3 Section 1Why Do I Need To Know This?

Because what you are depends upon what you eat . . . so we need to know what were eating and what that stuff is eating.

Because we are removing major amounts of organisms from various levels in ecosystems and causing serious disruption to food webs and food chains.

Because we can increase food production to feed more people without using toxic pesticides by understanding the importance of each and every trophic level in an ecosystem.

5Key Sections Ch. 3-1

Energy Flow In Ecosystems

Life Depends on the Sun

An Exception in the Rule Deep-Ocean Ecosystems

What Eats What

Respiration Burning The Fuel

Energy Transfers Food Chains, Food Webs, and Trophic Levels

Food Chains and Food Webs

Trophic Levels

How Energy Loss Affects An Ecosystem

6Energy Flow In Ecosystems

All organisms need energy in order to survive.

To fully understand an organism and its ecosystem, we need to understand how it gets its energy and how the energy flows in the ecosystem.

7Life Depends on the Sun

Almost all life depends either directly or indirectly for energy from the sun.

Plants, algae and some bacteria can turn solar energy directly into energy through a process called photosynthesis. These organisms are called producers.

When animals eat plants or other animals that ate plants, they are still getting their energy indirectly from the sun. These organisms are consumers.

8An Exception To the Rule Deep-Ocean Ecosystems

There is one known exception to the rule about all life depending on the sun, and that is at the very bottom of the deep ocean.

In 1977, scientists discovered that existed so deep that no sunlight could reach them.

The scientists discovered that the plants and animals got their energy from volcanoes erupting underneath the ocean!

They called this type of life chemosynthesis.

9What Eats What

Consumers that only eat producers are called herbivores.

Consumers that only eat other consumers are called carnivores.

Consumers that eat both producers and other consumers are called omnivores.

Consumers that get their nutrients by eating the dead remains of other organisms are called decomposers.

10Respiration Burning The Fuel

Photosynthesis is the chemical reaction used by producers to make food.

The chemical reaction is 6CO2 6 H20 Light Energy ? C6H12O6 6O2

Respiration is the process that consumers use to produce energy from the food they eat.

The chemical reaction is C6H12O6 6O2 ? 6CO2

6H20 Energy

They are opposite reactions!

11Energy Transfers Food Chains, Food Webs, and Trophic Levels

Every time one organism eats another organism, energy is transferred in an ecosystem.

Ecologists trace the transfer of energy in two ways

Food Chains These show the direct line of how the energy is transferred from one organism to another.

Food Webs These show the many feeding relationships between organisms in an ecosystem.

12Food Chains and Food Webs

Food chains are especially useful in showing direct cause and effect relationships in an ecosystem.

Food webs are useful in representing how an ecosystem truly works because most consumers usually eat more than one organism.

13Trophic Levels

Each level of energy transfer in an ecosystem is known as a trophic level.

As energy moves up each trophic level, about 90 of the energy is lost, leaving only about 10 of the energy available for the next level.

Therefore, the lowest trophic levels contain the largest population sizes and the highest trophic levels have the smallest population sizes.

Energy is lost in each trophic level because all the life functions for the organisms at that level (such as growing, moving, reproducing, etc.).

14How Energy Loss Affects And Ecosystem

When the amount of energy available at a lower level decreases, the amount of organisms that can be sustained at a higher trophic level also decreases and the number of trophic levels that can exist also decreases.

Humans are at the top of all trophic levels.

So, if we wipe out many lower tropic levels, we will reduce the number of people that can live on the planet and can wipe out many species that live at lower trophic levels.

15Ch. 3-2 The Cycling of Materials

Key Terms

Precipitation

Water Cycle

16California Content Standards for Science Addressed

Life Science

6(d) Students know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecosystem and how oxygen cycles through photosynthesis and respiration.

17Ch. 3 Section 2Why Do I Need To Know This?

Because every atom of every cell in your body has most likely been a part of another organism.

Because every atom of every molecule of food that you eat or drink has probably been eaten, drunk, or used by another living organism.

Because as long as the materials recycle, an ecosystem will stay in balance. When it no longer cycles from organism to organism, the ecosystem will collapse and die out.

18Key Sections Ch. 3-2

The Cycling of Materials

The Water Cycle

The Carbon Cycle

How Humans Are Affecting the Carbon Cycle

The Nitrogen Cycle

Closing the Nitrogen Cycle

19The Cycling of Materials

In every ecosystem, all materials get recycled.

All materials get recycled at various rates.

Some are very fast, while others can take millions of years.

Without the recycling of materials, all ecosystems would collapse when they ran out of limited resources.

There are many cycles in nature, but 3 of the most important are

The Water Cycle

The Carbon Cycle

The Nitrogen Cycle

20The Water Cycle

Water is essential for all life.

Although water changes form (from a solid to liquid to gas), the overall amount of water remains the same on the Earth.

The 3 main steps to the water cycle are

Evaporation

Condensation

Precipitation

The overall force driving the water cycle is the energy from the sun.

Water can be removed from the water cycle and stored underground as groundwater.

21The Water Cycle 22The Carbon Cycle

Carbon is also essential for all life on Earth.

Carbon is used to make up proteins, fats, and carbohydrates (all of which we need everyday).

When consumers eat producers, they take in the carbon they need.

During respiration, consumers give back carbon into the environment.

Some carbon gets stored underground as the remains of plants and animals get buried. This carbon will go onto become fossil fuels.

23The Carbon Cycle 24How Humans Are Affecting The Carbon Cycle

Fossil fuels, such as coal, oil and gasoline contain large amounts of carbon that has been stored underground.

As humans burn fossil fuels, we are emitting large amounts of carbon dioxide into the ecosystem, which is having a major effect on the worlds atmosphere and climate.

25The Nitrogen Cycle

Nitrogen is another essential element for life.

Nitrogen is used to make proteins, which is necessary for life.

Although 78 of the atmosphere is Nitrogen, only a special type of Nitrogen called Nitrates (NO3) can be used by most life forms on the planet.

In order to get Nitrogen, most bacteria depend upon bacteria to fix the Nitrogen in the atmosphere to make it useable at Nitrates.

The bacteria that fix the Nitrogen are called Nitrogen-fixing bacteria.

26Closing the Nitrogen Cycle

Once Nitrogen enters into the ecosystem through the nitrogen fixing bacteria, it mostly stays there.

Nitrogen in an ecosystem gets broken down by decomposers, such as fungi and bacteria.

However, some Nitrogen is returned to the atmosphere by different bacteria.

27The Nitrogen Cycle 28Ch. 3-3 How Ecosystems Change

Key Terms

Climax Community

Pioneers

Succession

29California Content Standards for Science Addressed

Life Science

6(a) Students know biodiversity is the sum total of different kinds of organisms and is affected by alterations of habitats.

6(b) Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size.

6(e) Students know a vital part of an ecosystem is the stability of its producers and decomposers.

30Ch. 3 Section 3Why Do I Need To Know This?

Because all ecosystems change over time.

So that we can understand the role of each organism in its ecosystem to know how it is helping the ecosystem change.

So that we can better respond to natural disasters and environmental problems by using succession to help fix the problem and restore a damaged ecosystem.

31Key Sections Ch. 3-3

How Ecosystems Change

Succession

Secondary Succession

Fire-Maintained Communities

Primary Succession

32How Ecosystems Change

All ecosystems change over time.

Over time, areas will change from a rocky landscape to a very well developed and stable community.

33Succession

Succession is the regular pattern of change in the species in a community.

Succession happens because as one species enters into an ecosystem, it alters the ecosystem to suit it.

As the species change the ecosystem, they make it more difficult for some organisms to live in the ecosystem and easier for others to live in it.

Eventually, an ecosystem reaches a stable and final community. This is called a climax community.

34Secondary Succession

Secondary succession occurs when a new community develops on the spot of a previously existing community.

This typically happens after a major natural disaster (such as a fire) or after an area has been cleared for human use.

Secondary succession happens rather rapidly (within about 150 years) because the soil and many of the necessary nutrients are already in place.

During secondary succession, grasses and flowers recover first. Then, over time, shrubs and trees move in, and finally trees take over, crowding out the plants and shrubs.

35Secondary Succession 36Fire-Maintained Communities

Many ecosystems depend upon natural fires to maintain themselves.

Some species, pine trees, for example, require the heat from a fire to release their seeds.

Many animals depend on natural fires to open up space for grasses and other producers to grow in order to feed upon them.

Fire helps to eliminate new species to the ecosystem to help maintain the stability of that ecosystem.

As a result, in some areas, firefighters allow naturally occurring fires to burn themselves out.

37Primary Succession

Primary succession occurs on surfaces where no previous ecosystem existed.

This is much slower process than secondary succession, typically taking thousands of years to happen.

The first organisms to move into the new area are called pioneers. Bacteria and lichens are two common pioneers.

The pioneers play an important role in succession because they turn raw material into useable resources for all species that follow them.

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